This invention relates to an intake control system for an engine, and more particularly to an improved induction system and control therefor that improves the performance of the engine throughout its entire speed and load ranges by selectively inducing turbulence in the intake charge.
As is well known, the design of the induction system for an engine has a substantial effect on its performance. Unfortunately, induction systems that provide good high-speed performance and maximum power outputs provide extremely poor running under low and mid-range conditions. The reason for this is that the induction system, in order to provide maximum output, should have high volumetric efficiency. This requires an induction system that delivers the charge into the combustion chamber at a relatively high velocity and with very low flow restriction and turbulence. However, this type of induction system causes the air charge to enter the combustion chamber at a very slow rate when running at low and mid-range speeds. In addition, the charge flows into the chamber in such a way that very little turbulence is generated. As a result, flame propagation is slow and poor performance, particularly in the areas of fuel economy and exhaust emission control, result.
In order to improve the performance throughout the entire speed and load ranges, various types of variable intake systems have been proposed. These systems are variable in effect, so that they function efficiently under both high- and low-speed conditions. Frequently, this variation in tuning of the induction system is achieved by varying the effective length of the induction system. These arrangements are very effective for their purpose.
However, the basic configuration of the ports which serve the engine with such variable systems is normally such that the port is substantially unrestricted and does not induce any swirl or tumble to the intake charge. As a result, even though the flow velocity may be increased at low speeds, insufficient turbulence is generated to the charge so as to achieve the desired flame propagation.
Other types of induction systems have been proposed that include flow modifying arrangements that are disposed in either the intake passage or the intake port adjacent the intake valve. These systems use a type of flow control valve which can be positioned so as to redirect the charge entering the combustion chamber under low speed and low load conditions to generate the desired type of turbulence. Again, these systems are effective for their purpose, but do not completely solve the problem of maintaining optimum efficiency under all running conditions.
It is, therefore, a principal object of this invention to provide an improved intake control system for an internal combustion engine.
It is a further object of this invention to provide an improved induction system for an engine that can improve the performance under all running conditions.
It is a further object of this invention to provide an induction system for an engine which provides not only variable tuning for varying engine speeds and loads, but also which can introduce tumble and/or swirl into the intake charge under certain running conditions so as to further increase the turbulence in the combustion chamber.
A system is disclosed in the copending application entitled "Intake Control System," Ser. No. 08/363,746, filed Dec. 23, 1994 in the names of Kenichi Sakurai, Masami Wada, and Masato Mishigaki and assigned to the assignee hereof wherein the induction system is provided with a variable effective length for tuning for different engine speeds and loads and also a control valve arrangement for generating turbulence in the combustion chamber under certain running conditions. Although that system is very effective, it is believed that further improvements in performance can be obtained.
Specifically, the arrangement shown in that application provide, in most embodiments, a control valve that controls the flow to the combustion chamber through a single intake passage. Hence, the control valve exerts an influence over the total charge that is flowing into the cylinder. When this is employed with multiple intake valves, as shown in that application, then only certain types of turbulence can be generated in the combustion chamber. Another embodiment is shown in that application wherein there are a pair of intake passage sections which serve different valve seats associated with a single combustion chamber and the control valve either permits or precludes flow through one of these intake passages. This arrangement also limits the amount and type of turbulence which can be generated in the combustion chamber.
It is, therefore, a principal object of this invention to provide an improved induction system for an engine wherein greater control is permitted over the induction system characteristics.
It is a further object of this invention to provide an improved induction control system for an engine and particularly one having multiple intake valves.
It is a still further object of this invention to provide an induction control system for an engine wherein the system can be tuned for different running conditions and wherein different types of flow conditions into the cylinder is possible under varying running conditions.
As will become apparent, a feature of this invention embodies an arrangement wherein the intake passage for each cylinder is divided into a pair of delivery sections which cooperate with different valves for that cylinder so as to provide a wider range of control. A throttle valve is provided in one of these intake passage sections and a flow control valve is provided in the other section. The use of both a throttle and a flow control valve permits a wider latitude in the flow conditions into the cylinder under varying speed and load ranges.
However, by utilizing such arrangements it is necessary to provide two separate controls for each of the valves and separate valve shafts for their operation.
This obviously complicates the engine and its control structure.
It is, therefore, a still further object of this invention to provide an improved control valve arrangement for the individual cylinders of an engine.
It is a further object of this invention to provide an improved and simplified control and throttle valve arrangement for separate passages serving the same combustion chamber of an engine.